雅鲁藏布江中上游藏布曲泥石流成因分析

Analysis on Causes of Debris Flow in Zangbuqu River in the Upper Reaches of Yalongzangbu River

该区位于青藏高原南缘地带，为构造活动强烈、山地上升和河流下切速率较快的地区，流域相对高差在４００～１５００ｍ左右，主谷比降在２°～３５°，为泥石流的形成提供了有利的地形条件；历次强烈的构造运动，第四纪冰川，冰缘及地表风化作用，形成有多种类型的大量松散沉积物，提供了泥石流产生和发展的物质基础；泥石流爆发高峰期７～８月的降水量占年降水量的６０％左右。在时段降水分布中，１０ｍｉｎ降水量，在羊八井为６．２ｍｍ，拉萨为７．６ｍｍ，１０ｍｉｎ降水量可占３０ｍｉｎ降水量的７２％～８１％，显示了高山带降水强度较大的特点。

The studied area is located in the south marginal belt of the Qingzang Plateau where the tectonic movement is exctensive, the mountain uplifting and river undercutting region are quickly,inner the basin,the gradient of gullies are always 22°～35°,the relative difference of height is 400～1 500m,these landscape conditons are advantageous to the formation of debris flow;nearly every extensive tectonic movenent, the quarternary glaciation,sub glaciation and surfacial weathering generated many kinds of loose deposits and formed the solid material foundation for formation and development of debris flow;the annual precipitation is about 450mm,among which the rainfall during summer occupies nearly 90 percent, the rainfall during frequently ocurring period of debris flow in July and Augest occupied 60 percent of the annual precipitation ,the 10 minutes rainfall intensity is 6.2mm and 7.6mm in Yangbajing and Lahsa respectively. The rainfall in studied area has the high intensity features of mountain area, in another word, the regional rainfall is quite favourable to formation and activity of debris flow.